Multi-point filtering liquid level detection methods and apparatus

Abstract

A method of detecting a level of a liquid in a well of a container. The method includes looking up an expected liquid level of the liquid in the well of a container; measuring and recording a measured liquid level of the liquid in the well; changing a level of the liquid in the well based upon an expected amount of the liquid to be added or removed; and calculating a next expected liquid level at least in part based on multi-point filtering. Apparatus for carrying out the method are provided, as are other aspects.

What is claimed is: 
     
       1. A method of detecting a level of a liquid in a well, comprising:
 looking up in a memory an expected liquid level of the liquid in the well; 
 ramping a probe into the well containing the liquid to a well depth; 
 measuring and recording a measured liquid level of the liquid from the ramping; and 
 calculating a next expected liquid level at least in part based on multi-point filtering and adjusting a depth of insertion of the probe into the well based on the next expected liquid level, wherein the next expected liquid level is used as the detected level of liquid in the well, further wherein the multi-point filtering comprises subtracting the expected liquid level from the measured liquid level to obtain a current normalized measured liquid level, calculating a current normalized filtered liquid level using an average filter, median filter, or mode filter on previous normalized measured liquid levels and the current normalized measured liquid level, and de-normalizing the current normalized filtered liquid level by adding the current normalized filtered liquid level to the expected liquid level to obtain the next expected liquid level. 
 
     
     
       2. The method of  claim 1 , wherein the calculating of the next expected liquid level is further based on applying an error correction to the next expected liquid level. 
     
     
       3. The method of  claim 2 , wherein the error correction is equal to an error times a gain. 
     
     
       4. The method of  claim 1 , wherein the calculating of the next expected liquid level further includes accounting for carryout. 
     
     
       5. The method of  claim 1 , wherein the multi-point filtering is accomplished using a median filter. 
     
     
       6. The method of  claim 5 , wherein the median filter uses a median value derived from 3 or more measured level values. 
     
     
       7. The method of  claim 6 , wherein the median filter uses the median value from 10 or more consecutively-obtained values. 
     
     
       8. The method of  claim 6 , wherein the median filter uses the median value from 15 or more consecutively-obtained values. 
     
     
       9. The method of  claim 1 , wherein the multi-point filtering is accomplished using a mode filter or an average filter. 
     
     
       10. The method of  claim 1 , comprising pre-filtering to remove an outlier value before applying the multi-point filtering. 
     
     
       11. The method of  claim 10 , wherein the pre-filtering comprises a pre-filter limit that is adjusted based on a state of a container containing the liquid. 
     
     
       12. The method of  claim 1 , comprising employing an adjustment limit so as to limit any adjustment from a next theoretical liquid level for the next expected liquid level. 
     
     
       13. The method of  claim 1 , comprising aspirating a volume of the liquid designated for a test prior to the calculating. 
     
     
       14. The method of  claim 1 , wherein the liquid in the well is a reagent liquid. 
     
     
       15. The method of  claim 1 , wherein the liquid in the well is water, a waste liquid, or a cleaning liquid. 
     
     
       16. The method of  claim 1 , comprising performing an aspiration quality verification after an aspiration. 
     
     
       17. The method of  claim 16 , comprising adjusting a probe position downward with an adjustment when the aspiration quality verification detects that air was aspirated. 
     
     
       18. The method of  claim 1 , wherein the measuring of the measured liquid level takes place during the ramping. 
     
     
       19. A method of detecting a level of a liquid in a well, comprising:
 looking up in a memory an expected liquid level of the liquid in the well of a container; 
 measuring and recording a measured liquid level of the liquid in the well; 
 changing a level of the liquid in the well based upon an expected amount of the liquid to be added or removed; and 
 calculating a next expected liquid level at least in part based on multi-point filtering and adjusting a depth of insertion of the probe into the well based on the next expected liquid level, wherein the next expected liquid level is used as the detected level of liquid in the well, further wherein the multi-point filtering comprises subtracting the expected liquid level from the measured liquid level to obtain a current normalized measured liquid level, calculating a current normalized filtered liquid level using an average filter, median filter, or mode filter on previous normalized measured liquid levels and the current normalized measured liquid level, and de-normalizing the current normalized filtered liquid level by adding the current normalized filtered liquid level to the expected liquid level to obtain the next expected liquid level. 
 
     
     
       20. A liquid level detection apparatus, comprising:
 a liquid level sensor configured to obtain liquid level measurements of a liquid in a well; 
 a memory configured to store an expected liquid level of the liquid in the well; and 
 a processor configured to receive the liquid level measurements and calculate according to a multi-point filtering module a next expected liquid level, wherein the multi-point filtering module is configured to subtract the expected liquid level from a current measured liquid level to obtain a current normalized measured liquid level, calculate a current normalized filtered liquid level using an average filter, median filter, or mode filter on previous normalized measured liquid levels and the current normalized measured liquid level, and de-normalize the current normalized filtered liquid level by adding the current normalized filtered liquid level to the expected liquid level to obtain the next expected liquid level. 
 
     
     
       21. The liquid level detection apparatus of  claim 20 , comprising a probe configured to aspirate the liquid.